Method and apparatus for applying a colorant to a thermoplastic to produce a visual effect

ABSTRACT

A visual effect, such as a granite-look, is produced in a thermoplastic product by directly applying a sufficient amount of at least one color-containing thermoplastic resin system to the surface of an extruded sheet of a thermoplastic resin. The color-containing thermoplastic resin system is applied onto the extruded sheet after it emerges from the die and prior to it entering the rollstack.

FIELD OF THE INVENTION

[0001] The present invention relates to methods and apparatuses forproducing visual and other surface effects in a finished thermoplasticproduct by directly applying at least one color-containing thermoplasticresin system to at least one surface of an extruded thermoplasticsubstrate. The present invention also relates to the finished articles.

BACKGROUND OF THE INVENTION

[0002] In the thermoplastic molding industry, the color and surfaceaesthetics of the final molded product dramatically influences the enduser's view of that product and, in turn, these ultimately dictate howwell it will sell. The ability to provide unique or enhanced colors orother surface aesthetics can dramatically increase both the variety ofapplications for which such a thermoplastic will be accepted and alsoallows the molded product to be distinguished from its competition.

[0003] Some of the more desirable conventional visual effects aretypically known as graining, mottling, blotching, marbling, streakingand variegation. One highly desirable aesthetic appearance forthermoplastic sheet materials is that of natural granite. Thisparticular visual effect has been generally referred to in the art aseither “granite-look” or “granite-like.”

[0004] Granite-look and other surface effects have typically beengenerated in the thermoplastic art by incorporating some form ofadditive into the thermoplastic resin system prior to molding orextrusion. Such methods exhibit several significant drawbacks.

[0005] While granite-look articles have been extremely desirable,previous methods for preparation of granite-look thermoplastic productshave typically employed large diameter pigments or large agglomerationsof smaller pigments within the molded resin itself. The loaded resin isthen processed in such a manner that these pigments or pigmentagglomerates are visible. Because most commercially-available pigmentsare of very small size, preparation of large particle sizes oragglomerates is difficult and expensive. Further, controlling particlesize during currently used methods for manufacture, specifically,compounding by extrusion or casting, is problematic.

[0006] It will also be appreciated by the skilled artisan that virtuallyany additive that is placed in a thermoplastic resin system primarily togenerate an aesthetic effect will compromise the physical properties ofthe finished product. Particularly, when dealing with opaquethermoplastics, both the nature and quantity of materials employed inthe art to produce these aesthetic effects have caused significantdecreases in important physical properties, such as impact strength andweatherability. Further, the nature and quantity of the materialspreviously employed in the art (once again, especially in opaquethermoplastics) have also created some significant processing problems;when sufficient amounts of certain additives are employed in order togenerate a granite-like appearance in a conventional opaquethermoplastic resin system, these same materials create flowinstabilities that can dramatically narrow or shift the process window.

[0007] One current method of producing granite-look engineeringthermoplastics is to load the thermoplastic resin with a hightemperature material such as a thermoset. While loading a thermoplasticresin with a high temperature material can produce desirable visualeffects, the loading level that is needed to provide the desired surfaceeffect results in both adverse changes to the process window and also afinal product that is far too brittle for most applications.

[0008] Another art-disclosed example of producing granite-lookengineering thermoplastics employs an additive mixture containing:chopped nylon (or polyester fibers) of the desired colors; titaniumdioxide; and a metallic soap dispersant. (See U.S. Pat. No. 5,407,988,issued Apr. 18, 1996 to Gary J. Kogowski, incorporated herein byreference.) This mixture is admixed with a thermoplastic resin systemprior to extrusion or injection molding. The fibers coalesce duringprocessing to form specks within the thermoplastic matrix and generatean improved granite-like appearance. Further, in employing this system,no fibers are typically detected in the finished product after extrusionor injected molding. However, there is a limitation on the amount ofsuch an additive mixture that can be employed without the processingwindow being narrowed and/or an associated reduction in importantphysical properties.

[0009] Because employing such additives in injection or extrusionmolding resin systems have such a negative impact on both processing andphysical properties, the art has also employed casting-type molding.While casting addresses some of the processing concerns discussed above,it does not eliminate them all together. Other art-disclosed ways ofgenerating such surface aesthetics on thermoplastics include, forexample, molding-in surface texture (alone or in combination withincorporating additives to the base resin prior to molding as discussedabove). Another method involves flexo or gravure printing of the desiredimage or aesthetic on a thin film and then laminating the thin film tothe sheet thermoplastic material. While printing and photographing suchpatterns result in accurate reproductions of the desired effect, thisprocess suffers from the significant drawback of having the overallphysical properties of the printed film typically being the controllingfactor in the scope of applications. Further, the width of films thatcan be effectively used as a substrate for such methods is limited.

[0010] The present invention overcomes many of these disadvantages bydirectly applying at least one compatible color-containing thermoplasticresin system to at least one surface of a thermoplastic after molding orextrusion, thus achieving a visual effect, such as a granite-look, whileavoiding or minimizing any adverse effects on the physical properties orprocessing of the thermoplastic typically associated with art-disclosedmethods.

SUMMARY OF THE INVENTION

[0011] It is an object of the present invention to simply andefficiently produce a granite-like or other surface effect on anextruded thermoplastic sheet product by directly applying a compatiblecolor-containing thermoplastic resin system to at least one visiblesurface of the extruded thermoplastic sheet. A compressive force is thenapplied to the treated surface. Especially useful resin systems for useas the treated substrate in the present invention include styreniccopolymers such as acrylonitrile-styrene-acrylate andacrylonitrile-butadiene-styrene. The methods of the present inventionachieve highly desirable visual effects, particularly a granite-likeappearance, while minimizing any adverse effects on processing orphysical properties, especially impact strength. The desired surfaceeffect is achieved by the interaction of the color-containingthermoplastic resin system and the extruded thermoplastic sheet, withoutthe necessity of using an embossing mechanism, as is common to prior artsurface effect thermoplastics which rely on a difference in theconcentration of pigment between embossed and non-embossed areas toachieve the desired effect.

[0012] It is another object of the present invention to provide both anapparatus for carrying out such methods and the articles producedthereby.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a diagrammatic illustration of an apparatus of thepresent invention for directly applying a colorant onto the surface ofan extruded sheet of a thermoplastic, in accordance with one aspect ofthe present invention.

[0014]FIG. 2 is a photomicrograph of a cross-sectional view of anextruded sheet of a thermoplastic that has had a color-containingthermoplastic resin system directly applied onto the surface of theextruded sheet, in accordance with one aspect of the present invention.

DETAILED DESCRIPTION

[0015] The methods and apparatuses of the present invention produce agranite-like appearance or other visual or textural effect on thesurface of a sheet-like molded thermoplastic product. The method iscarried out by first extruding or otherwise molding at least onethermoplastic in sheet form. Next, a color-containing thermoplasticresin system that is compatible with at least part of the extrudedthermoplastic surface is used to treat at least one visible surface,preferably by direct application. A compressive force is then applied tothe treated surface. The surface of the extruded thermoplastic ispreferably maintained at a temperature sufficient to allow thecolor-containing system to react with, bond with or otherwise adhere tothe surface of the treated thermoplastic substrate to achieve thedesired visual or textural effect. No embossing mechanism is used in themethod of the invention. In one embodiment, the color-containing systemis preferably maintained at a temperature at or near the softening pointof the thermoplastic it employs.

[0016] The advantages associated with this surface treatment ofthermoplastic include the fact that the physical properties (e.g.,impact strength; modulus of elasticity; weatherability; etc.) of thefinal product are not negatively effected. Further, the methods of thepresent invention avoid the processing problems commonly associated withmethods where the additives that produce the aesthetic surface effectare added to the substrate resin system prior to processing. Additionaladvantages are the reduction in manufacturing costs and the ease ofproduction.

[0017] The overall quality of the desired effect is also improved. Inthis regard, because the processes and methods of the present inventionprovide for surface treatment of the molding, they are continuous innature: the treatment of the surface can be continuously monitored anddynamically adjusted on an ongoing basis, in contrast to static priorart methods that required addition prior to molding.

[0018] By the terms “granite-look” and “granite-like,” as used herein todescribe the surface of a thermoplastic, is meant that at least onefinal visible surface of the thermoplastic sheet material so describedpossesses an appearance that mimics, simulates, or otherwise conjures upthat of naturally occurring granite.

[0019] By the terms “color-containing thermoplastic resin system” and“color-containing system” as used herein is meant a system thatcomprises at least two elements: (1) at least one pigment or dye; and(2) at least one thermoplastic material, preferably one that iscompatible with a substrate thermoplastic resin. Other compounds,materials or agents may be employed in this system as well, especiallythose conventionally used in coloring thermoplastic resins or informulating color concentrates. By way of example (but without anysuggestion of limitation) the color-containing thermoplastic resinsystems useful in the present invention may additionally employ aplurality of organic or inorganic pigments, dyes, or mixtures thereof.These may be incorporated into the thermoplastic resin as conventionaldry or liquid color concentrates, superconcentrates, or precolored resinsystems.

[0020] The thermoplastic material employed in the color-containingsystem may be any thermoplastic material, but preferably includes aresin that is compatible with at least one of the thermoplasticsemployed in the substrate to be treated. By “compatible,” as that termis used herein to describe the thermoplastic material employed in thecolor-containing system, is meant that the thermoplastic will, under theprocessing conditions employed, substantially bond with, react with, orotherwise adhere to the treated thermoplastic surface. Without intendingto be bound by theory, this reaction, binding or other adherence can bemechanical, physical, chemical, or any combination thereof. Suchcompatibility is typically characterized as both a chemical bond (withlittle or no crosslinking), hydrogen bonding, and/or mechanicalretention. By way of a nonlimiting example, when the substrate surfaceto be treated comprises acrylonitrile-styrene-acrylate (ASA) materials,ASA or styrene-acrylonitrile would be preferred thermoplastic materialsfor use in the color-containing system. Other non-limiting examples arediscussed below.

[0021] The color-containing system may also include one or more of theadditives conventionally employed in color concentrates,superconcentrates, liquid colors, precolored resins, dry colors, orthermoplastic molding resin systems in general. Examples of suchadditives include, without limitation, antistatic agents, heatstabilizers, waxes, plasticizers, antioxidants, carbon blacks or otherconductive agents, flame retardants, light stabilizers, ultravioletstabilizers, meta-stable compounds, viscosity modifiers, antidustingagents, and the like.

[0022] As discussed above, the thermoplastic materials in thecolor-containing systems of the present invention are preferablycompatible with the thermoplastics used to mold or extrude the substrateto be treated with the color-containing system. It will be appreciatedthat the preferred candidates are thermoplastics that are the same, ornearly the same, as those employed in an unblended substrate. Forblended substrates, the following factors are important: (1) chemicalcomparability between the thermoplastic materials in thecolor-containing system and the thermoplastics used to mold or extrudethe substrate to be treated with the color-containing system; and (2)similar softening or processing temperatures between the thermoplasticmaterials in the color-containing system and the thermoplastics used tomold or extrude the substrate to be treated with the color-containingsystem.

[0023] Examples of typical thermoplastic resins to be employed incolor-containing systems include those thermoplastics generally referredto as engineering thermoplastics. Examples of engineering thermoplasticsinclude polyacetals; polystyrenes, including high-impact polystyrenesand styrenic copolymers such as acrylonitrile-styrene-acrylate (ASA),acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitriles (SAN), andstyrene-maleic anhydrides (SMA); polyamides (nylons); polycarbonates;polyesters such as polyethylene terephthalates and polybutyleneterephthalates; polyolefins such as polyethylene and polypropylenehomopolymers and copolymers; polyurethanes; polyvinyl chlorides;acrylics; and mixtures thereof.

[0024] Examples of preferred material are as follows. For an ASAsubstrate, an ASA or SAN thermoplastic is preferred as the thermoplasticmaterial in the color-containing system. For an ASA/ABS substrate, anASA or SAN thermoplastic is also preferred as the thermoplastic materialin the color-containing system. For an ABS substrate, an ABS, ASA, orSAN thermoplastic is preferred as the thermoplastic material in thecolor-containing system.

[0025] The types of thermoplastics that are particularly useful toproduce the molded or extruded sheets in the practice of the presentinvention are generally engineering thermoplastics that may be molded orformed into sheets by extrusion or other molding processes andapparatuses, either alone or as blends. Illustrative engineeringthermoplastics include each of those engineering thermoplastics listedabove as suitable for the thermoplastics for the color-containingsystems. It will be appreciated by the skilled artisan that theselection of the thermoplastic that is to be molded into sheet form andthen act as the substrate to be treated with the color-containingthermoplastic resin system will be influenced primarily by the end-useof the finished product. Important factors for selection of thethermoplastic material for the color-containing system include not onlyits compatibility with the thermoplastic selected for the substrate, asalready discussed, but also, again the end-use of the finished product.

[0026] One commercially-available polyacetal useful in the practice ofthe present invention for treatment as the substrate is a materialmarketed under the trademark ULTRAFORM® (BASF Corporation, Mount Olive,N.J.). ULTRAFORM® brand material is a polyoxymethylene copolymer (POM)that exhibits an outstanding combination of strength, rigidity andtoughness, extremely low water absorption, outstanding resilience, gooddimensional stability, high fatigue strength, favorable tribologicalcharacteristics, and good chemical resistance.

[0027] Other commercially-available materials useful in the practice ofthe present invention for treatment as the substrate are polyamidesmarketed under the trademarks ULTRAMID®, ULTRAMID®A, ULTRAMID®B,ULTRAMID®C, and ULTRAMID®T (BASF Corporation, Mount Olive, N.J,). All ofthese polyamides exhibit good dimensional stability, good heatresistance, high tensile strength and stiffness, good toughness,excellent processability, excellent finish, and good chemicalresistance.

[0028] One commercially-available polybutylene terephthalate useful inthe practice of the present invention is ULTRADUR®B (BASF Corporation,Mount Olive, N.J.). ULTRADUR®B brand materials exhibit high rigidity andstrength, high resistance to heat distortion, low water absorption, gooddimensional stability, good dielectrical properties, good chemicalresistance, good toughness even at low temperatures, and good outdoorweatherability and resistance to high-temperature aging.

[0029] The styrenic copolymers are particularly useful for treatment asthe substrate in the practice of the present invention. Their usefulnessis due to their excellent physical properties. For example, both ASA andAES possess excellent weatherability.

[0030] Styrenic copolymers are thermoplastics that are formed by thereaction of two or more different monomers, one of which is styrene. Themost preferred type of styrenic copolymer which isacrylonitrile-styrene-acrylate (ASA) copolymer, which may be employed,alone or as a blend with ABS. ASA copolymers are well known commercialthermoplastics. ASA copolymers are random amorphous terpolymers producedeither by a mass copolymerization process or by graftingstyrene-acrylonitrile to an acrylic elastomer backbone. ASA copolymersare characterized as outdoor weatherable and UV-resistant products thatprovide an excellent combination of color stability and propertyretention after outdoor exposure. ASA copolymers have many uses, forexample, in bath tubs, shower stalls, swimming pool steps, and spas. ASAcopolymers can also be used in multilayer applications or in coextrusionapplications.

[0031] In accordance with one highly-preferred embodiment of the presentinvention, the ASA copolymer employed is a material marketed under thetrademark LURAN® S (BASF Corporation, Mount Olive, N.J.). LURAN® S brandmaterial exhibits outstanding outdoor weatherability, excellent colorretention, good impact resistance, great toughness and rigidity, goodheat stability, and good chemical resistance. Additionally, LURAN® Sbrand ASA is available in a variety of colors. It will be appreciatedthat because the colored LURAN® S brand materials are not transparent, agranite-look appearance is most effectively achieved by modifying only asurface layer of the sheet.

[0032] Another styrenic copolymer useful in the substrate isstyrene-acrylonitrile (SAN). One useful commercially-availablestyrene-acrylonitrile useful in the practice of the present invention ismarketed under the trade name LURAN® (BASF Corporation, Mount Olive,N.J.). LURAN® brand material exhibits high clarity and gloss, rigidityand toughness, and excellent chemical resistance.

[0033] Additionally, styrenic copolymers employed in the presentinvention may be blended with other thermoplastics. One usefulcommercially-available acrylonitrile-styrene-acrylate blend useful inthe practice of the present invention is an ASA marketed under thetrademark LURAN® S ‘C’ (BASF Corporation, Mount Olive, N.J.). LURAN® S‘C’ brand ASA is a blend of acrylonitrile-styrene-acrylate andpolycarbonate. LURAN® S ‘C’ brand ASA exhibits high heat resistance,good impact resistance and dimensional stability, resistance toyellowing under heat and UV radiation, and outstanding resistance tohigh temperature aging.

[0034] Another important type of styrenic copolymer that may be employedin the substrate sheet is acrylonitrile-butadiene-styrene (ABS)copolymer. ABS plastics are typically two-phase systems.Styrene-acrylonitrile (SAN) forms the continuous matrix phase. Thesecond phase is composed of dispersed polybutadiene particles, whichhave a layer of SAN grafted onto their surface. The layer of SAN at theinterface makes the two phases compatible. ABS copolymers have manyuses, for example, in refrigerator linings, machine housings, instrumentpanels, pipes, countertops, sinks, and bathtubs. ABS copolymers can alsobe used in multilayer applications, as well as coextrusion applications.

[0035] One useful commercially-available type ofacrylonitrile-butadiene-styrene useful in the practice of the presentinvention is marketed under the trademark TERLURAN® (BASF Corporation,Mount Olive, N.J.). Another useful commercially-available type ofacrylonitrile-butadiene-styrene useful in the practice of the presentinvention is an ABS material marketed under the trademark TERLUX® (BASFCorporation, Mount Olive, N.J.). TERLUX® brand ABS is a blend of methylmethacrylate and acrylonitrile-butadiene-styrene that exhibits excellenttransparency, toughness, good chemical resistance, and good stresscracking resistance.

[0036] Another type of useful styrenic copolymer isacrylonitrile-ethylene-styrene (AES) copolymer.

[0037] The types of thermoplastics that are particularly suitable fortreatment as the substrate in the practice of the present inventioninclude, without limitation: ASA copolymers; ABS copolymers; AEScopolymers; polyvinyl chloride (PVC); blends of polycarbonate (PC)/ABScopolymers in the ratio of about 5:95 to about 95:5 weight percent ofPC:ABS; blends of ABS copolymers/nylon in the ratio of about 5:95 toabout 95:5 weight percent ABS:nylon; blends of PC/ASA copolymers in theratio of about 5:95 to about 95:5 weight percent PC:ASA; blends ofPVC/ASA copolymers in the ratio of about 20:80 to about 80:20 weightpercent PVC:ASA; and blends of ASA copolymers/AES copolymers in theratio of about 20:80 to about 80:20 weight percent ASA:AES. Thesethermoplastics and thermoplastic blends are preferred in part due totheir excellent weatherability. Especially preferred for treatment asthe substrate in the practice of the present invention are ASAcopolymers.

[0038] Colorants have been previously used in conjunction with manythermoplastics in order to impart a visual effect, such as agranite-look, to the thermoplastic by incorporation directly into thebase resin prior to molding, and these same colorants and materials maybe employed in the practice of the present invention when preparing acolor-containing thermoplastic resin system. Colorants are generallydefined as substances used to impart to or augment color in a resin orother material and are conventionally classified as pigments and dyes.When employed in engineering thermoplastics, the colorants are typicallyadded in the form of color concentrates that are introduced into thethermoplastic resin through, for example, compounding. Typical colorconcentrates include one or more thermoplastic resins, which arepreferably compatible with the resin system to be colored (or itssurface), and one or more pigments or dyes. In this sense, thethermoplastic resin acts as a binder or carrier for the pigment.

[0039] Art-disclosed color concentrates have taken the form of pellets,cubes, beads, wafers, powders or micro-beads. Color concentratesconventionally have a pigment loading of from about 10% by weight toabout 80% by weight, and typically from about 30% by weight to about 60%by weight, based upon the weight of the color concentrate. Preferably,the color concentrates have employed a pigment loading of up to about80% by weight, and preferably at least about 50% by weight. The dye orpigment concentration will vary depending upon the selection of dye orpigment and binder.

[0040] Alternatively, two or more colorants or color concentrates may beblended or dry mixed to obtain the desired color and applied as thecolor-containing system of the present invention. Color concentrates arereadily available commercially from a number of companies, includingReedSpectrum (Holden, Mass.), Uniform Color Company (Holland, Mich.),Americhem, Inc. (Cuyahoga Falls, Ohio), and Holland Colors Americas Inc.(Richmond, Ind.).

[0041] Typically, a color concentrate is formed by thoroughly mixing thecolorant or mixture of colorants with the thermoplastic material. Thecolorant-thermoplastic mixture is then formed, through molding, casting,or extrusion, into the desired shape and processed into a finished colorconcentrate.

[0042] In accordance with one highly preferred embodiment of the presentinvention, a color-containing thermoplastic resin system is applieddirectly onto at least one surface, preferably the top surface, of anextruded or otherwise shaped article, especially an extruded sheet, ofthermoplastic resin after emerging from the die or mold and prior toentering a rollstack.

[0043] In a preferred embodiment of the present invention, thecolor-containing system preferably comprises at least one conventionalcolor concentrate in the form of at least one pigment and at least onethermoplastic resin binder or carrier which is compatible with athermoplastic resin comprising the surface of the extruded shape. Morepreferably, a colored styrenic copolymer, and most preferably a coloredASA copolymer (e.g., LURAN® S), is employed as the thermoplastic resinbinder or carrier. The colorants employed in the color-containing systemmay be comprised of one or more different individual pigments or colors.

[0044] Additionally, it should be appreciated that the thermoplasticresin to be extruded may also be colored with one or more colorants.

[0045] The color-containing thermoplastic resin systems employed arepreferably applied to the surface of the extruded sheet in the form ofparticles. The color-containing thermoplastic resin systems arepreferably cooled (preferably with liquid nitrogen) to a temperaturebelow about −70° C. and then ground to a desired particle size so as tomaximize the surface area. A particular color-containing thermoplasticresin system in the form of particles may be mixed with color-containingthermoplastic resin systems of other colors or textures to produce adesired visual effect, color or shade. Preferably, the particle size ofthe ground colorant will range from about 5 microns to about 3000microns. Expressed in terms of U.S. Standard mesh size, the particlesize of the ground colorant will preferably range from about −6 to about+5000 U.S. Standard mesh size, more preferably from about −10 to about+5000 U.S. Standard mesh size, still more preferably from about −14 toabout +5000 U.S. Standard mesh size, and most preferably from about −16to about +5000 U.S. Standard mesh size. All of the ground colorantparticles preferably have an average aspect ratio of about 1.7.

[0046] As noted above, and without being bound to a particular theory ofthe operation of the present invention, it is believed that the use ofcolored thermoplastic resins as color imparting particles improves thebonding of the color imparting particles to the surface of the extrudedthermoplastic resin due to the similar chemical and physical propertiesof the color-containing thermoplastic resin system and the extrudedthermoplastic resins.

[0047] The extrusion process, which converts plastic material into aparticular form (such as a sheet), uses an extruder to meltthermoplastic pellets or powder and force the resulting melt through adie. The extruded shape comes out of the die at a continuous rate and isthen cooled, typically by being transported through a rollstack. Thecooled, extruded shape may then be transported through a set offinishing rolls for further processing.

[0048] In accordance with one embodiment of the present invention, therollstack and the thermoplastic resin to be extruded are preferably setto slightly higher temperatures than normal operation to assure that thecolorants, applied before the rollstack, soften and bond to the matrixof the extruded thermoplastic resin. Typically, the rollstack is set toa temperature in the range of about 150° F. to about 200° F. for normaloperation with respect to ASA, ABS, or ASA/ABS substrates. It will beappreciated by the skilled artisan that the typical temperature of therollstack for normal operation will be dependent in part on the extrudedthermoplastic resin, as well as the thermoplastic materials employed inthe color-containing system. However, in accordance with one preferredembodiment of the present invention, the rollstack is preferably set toa temperature in the range of about 180° F. to about 210° F.,particularly when the substrate to be extruded is an ASA, ABS, orASA/ABS substrate. Again, it will be appreciated by the skilled artisanthat the typical temperature of the rollstack for warmer than normaloperation will be dependent in part on the extruded thermoplastic resin,as well as the thermoplastic materials employed in the color-containingsystem. Without being bound to a particular theory of the operation ofthe present invention, it is believed that the use of a slightly warmerthan normal rollstack improves the bonding of the color-containingsystem to the surface of the extruded thermoplastic resin.

[0049] Typically, the thermoplastic resin to be extruded is maintainedat a temperature in the range of about 430° F. to about 440° F. fornormal operation. However, in accordance with one preferred embodimentof the present invention, the thermoplastic resin to be extruded ispreferably maintained at a temperature in the range of about 440° F. toabout 480° F. It will be appreciated that the maintenance temperature ofthe thermoplastic resin will depend on the softening temperature of theparticular thermoplastic or thermoplastic blend.

[0050] The color-containing system is generally maintained at atemperature in the range of room temperature (i.e., ambient temperature)to about 280° F. It is important in most embodiments that thecolor-containing thermoplastic resin system not be maintained at atemperature substantially above the softening temperature of theparticular thermoplastic(s) employed, as this may cause the individualparticles to agglomerate.

[0051] Although the present invention is primarily directed to producinga granite-look or granite-like appearance in thermoplastic products, itshould be appreciated that the methods and apparatuses of the presentinvention are capable of producing numerous other visual effects inconjunction with various color combinations. For example, other visualeffects that can be achieved include, without limitation, graining,mottling, blotching, marbling, streaking, and variegation.

[0052] The intensity of the granite visual effect is generallyproportional to the amount of colorant that is placed on the surface ofthe sheet, as well as the randomness of the pattern in which thecolorant is applied. It should be appreciated that the weightpercentages of the extruded thermoplastic resin and the color-containingthermoplastic resin system in the finished product will vary due to thetotal sheet thickness and the intensity of the visual effect achieved.

[0053] Referring to FIG. 1, there is generally illustrated an apparatusfor directly applying at least one color-containing system to thesurface of an extruded sheet of thermoplastic resin, in accordance withone aspect of the present invention. The extruder 1 produces asubstantially flat sheet of thermoplastic resin 2 (e.g., ASA copolymer).As the sheet of thermoplastic resin 2 exits the extruder 1, a pluralityof colorant particles 3 are applied to a surface of the sheet ofthermoplastic resin 2. In this illustration, the colorant particles 3are being applied to the top surface of the sheet of thermoplastic resin2. However, it should be appreciated that, if desired, color-containingsystem particles 3 may also be directly applied to the bottom surface ofthe sheet of thermoplastic resin 2.

[0054] The color-containing system application system includes anysuitable receptacle and delivery system, such as a manifold 4, or atransfer sheet. Although one application system is illustrated in theFigure, multiple color-containing system application systems arecontemplated and may be preferred for certain embodiments of theinvention. The manifold 4 distributes the color-containing system overthe surface of the sheet of thermoplastic resin 2, but thecolor-containing system particles 3 need not necessarily be evenlydistributed. The color-containing system particles 3 are discharged fromthe manifold 4 through an opening 5. With respect to opening 5, avariable opening design may be employed. Additionally, an optionalvibrator 6 may be employed to loosen any color-containing systemparticles 3 lodged in the manifold 4 or opening 5. With respect to thevariable opening design mentioned above, opening 5 may include twosliding screens that have the same opening size. When the openings lineup, the larger size color-containing system particles 3 will passthrough along with the smaller ones. When the openings are not aligned,only the smaller sizes will pass through. By varying the frequency ofthe sliding screens, a more randomized visual effect can be obtained.

[0055] Optionally, a pan 7 (or any other suitable receptacle) under thesheet of thermoplastic resin 2 could catch overflow of thecolor-containing system particles 3 from the edge of the sheet ofthermoplastic resin 2 for recycling back to the manifold 4.

[0056] Finally, a rollstack 8 with an upstack arrangement (in otherwords, the extruded sheet starting between the lower two rolls and goingupward) assists in the adherence of the color-containing system to thetop or finished surface of the sheet of thermoplastic resin 2. However,it is envisioned that any suitable rollstack arrangement may be used inaccordance with the present invention, provided that a sufficient amountof at least one color-containing system adheres to the sheet ofthermoplastic resin 2.

[0057] It should be appreciated that by applying the color-containingsystem particles 3 only to the surface of the sheet of thermoplasticresin 2, the negatives associated with placing additives in the systemwhich is used to mold the resin 2 are minimized, as compared to addinghigher melt particles throughout the sheet of thermoplastic resin 2 byputting the color-containing system through the extruder 1 with thethermoplastic resin 2.

[0058] In accordance with one embodiment of the present invention, athermoplastic product is produced in which a cross-sectional viewreveals a thermoplastic matrix wherein the surface portion, layer orzone of the matrix contains color-containing system and the remainingportion, layer or zone of the matrix is substantially free of thecolor-containing system. In other words, there are two distinct layers,zones, or phases visible. Referring to FIG. 2, a first phase 100,corresponding to the surface of the thermoplastic, contains acolor-containing thermoplastic resin system and a second phase 200,corresponding to the rest of the thermoplastic matrix, is free of thecolor-containing thermoplastic resin system.

[0059] An example of a method for producing an article in accordancewith one aspect of the present invention, is presented below:

EXAMPLE

[0060] A black color concentrate (11563-T1 Black) was obtained fromAmerichem (Cuyahoga Falls, Ohio), and was used as one component of thecolor-containing thermoplastic resin system. The 11563-T1 Blackcontained about 20-30 weight percent of carbon black in a SAN(styrene-acrylonitrile copolymer) binder. A colored LURAN® brand ASAcopolymer, LURAN® S 797 SEUV White 00260 (BASF Corporation, Mount Olive,N.J.) was used as another component of the color-containingthermoplastic resin system. The LURAN® S brand LURAN® S 797 SEUV White00260 pellets were used to provide a contrasting color. The 11563-T1Black and the LURAN® S brand LURAN® S 797 SEUV White 00260 pellets werepresent in a 1:1 weight ratio. A LURAN® brand ASA copolymer, LURAN® S797 SEUV Gray 33647 (BASF Corporation, Mount Olive, N.J.), was used asthe base material, also referred to as the main resin component, of thesheet that was extruded. The pellets of black and white colorconcentrate were ground with a mill containing a 2.0 millimeter screento obtain a desired size of color imparting particles, preferably in therange of 5 to 3000 microns. The color concentrate pellets were cooledwith liquid nitrogen for easier grinding. The ground materials (blackand white color imparting particles) were randomly mixed into a cup fordistribution onto the surface of the LURAN® S brand LURAN® S 797 SEUVGray 33647 thermoplastic resin as it emerged from the sheet die of anextruder. In order to promote bonding, the surface of the rollstack wasset at about 190° F. and the temperature of the LURAN® S brand LURAN® S797 SEUV Gray 33647 thermoplastic resin as it exited the die was set at440° F. Without being bound to a particular theory of the operation ofthe present invention, it is believed that the black and white colorimparting particles were appropriately bonded to the LURAN® S 797 SEUVGray 33647 by softening prior to or in the nip area of the rollstack.The extruded sheet was then transported through the rollstack, cut, andprocessed into a finished article. The finished article was a uniformlyflat sheet having a granite-look appearance on the top surface of thesheet. A cross-sectional view of the sheet revealed a thermoplasticmatrix wherein the surface portion, layer or zone of the matrixcontained the color-containing thermoplastic resin system and theremaining portion, layer or zone of the matrix was substantially free ofthe color-containing thermoplastic resin system. The finished article isexpected to possess excellent weatherability based on the thermoplasticmaterials employed in both the base material and the color-containingthermoplastic resin system. .

[0061] It should be appreciated that the rate at which the colorimparting particles of the color-containing thermoplastic resin systemare distributed onto the surface of the extruded thermoplastic resin isdependent in part on the intensity of the visual effect to be achieved.Typically, the faster the rate of distribution, the more intense thevisual effect. Additionally, the intensity of the visual effect can beaffected by altering or varying the speed at which the extrudedthermoplastic resin exits the die of the extruder. However, it should benoted that the application of too much color-containing thermoplasticresin system onto the surface of the extruded thermoplastic resin cancause streaking on the surface due to accumulation at the rollstack.

[0062] The foregoing description is considered illustrative only of theprinciples of the invention. Furthermore, because numerous modificationsand changes will readily occur to those skilled in the art, it is notdesired to limit the invention to the exact construction and processshown as described above. Accordingly, all suitable modifications andequivalents that may be resorted to that fall within the scope of theinvention as defined by the claims that follow.

What is claimed is:
 1. A method for producing a granite-like appearanceor other visual or textural effect on a sheet-like molded thermoplasticproduct, comprising the steps of: extruding at least one thermoplasticin sheet form, said extruded thermoplastic having at least one visiblesurface; providing a color-containing thermoplastic resin systemcomprising at least one thermoplastic resin that is compatible with saidextruded thermoplastic; applying said color-containing system to saidvisible surface of said extruded thermoplastic to produce a treatedvisible surface; and applying a compressive force to said treatedvisible surface of said extruded thermoplastic.
 2. A method inaccordance with claim 1, wherein said surface of said extrudedthermoplastic is maintained at a temperature sufficient to allow saidcolor-containing system to adhere or bond to said surface of saidthermoplastic during said method.
 3. A method in accordance with claim1, wherein said compressive force is sufficient to promote adherence ofsaid color-containing system to said surface of said extrudedthermoplastic.
 4. A method in accordance with claim 1, wherein saidextruded thermoplastic is selected from the group consisting ofpolyacetals, acrylonitrile-styrene-acrylates,acrylonitrile-butadiene-styrenes, acrylonitrile-ethylene-styrenes,styrene-acrylonitriles, styrene-maleic anhydrides, nylons,polycarbonates, polybutylene terephthalates, polyethylenes,polypropylenes, polystyrenes, polyurethanes, polyvinyl chlorides,acrylics, and mixtures thereof.
 5. A method in accordance with claim 1,wherein said extruded thermoplastic is selected from the groupconsisting of: acrylonitrile-styrene-acrylate copolymers;acrylonitrile-butadiene-styrene copolymers;acrylonitrile-ethylene-styrene copolymers; polyvinyl chloride; blends ofpolycarbonate and acrylonitrile-butadiene-styrene copolymers in theratio of about 5:95 to about 95:5 weight percent; blends ofacrylonitrile-butadiene-styrene copolymers and nylon in the ratio ofabout 5:95 to about 95:5 weight percent; blends of polycarbonate andacrylonitrile-styrene-acrylate copolymers in the ratio of about 5:95 toabout 95:5 weight percent; blends of polyvinyl chloride andacrylonitrile-styrene-acrylate copolymers in the ratio of about 20:80 toabout 80:20 weight percent; and blends of acrylonitrile-styrene-acrylatecopolymers and acrylonitrile-ethylene-styrene copolymers in the ratio ofabout 20:80 to about 80:20 weight percent.
 6. A method in accordancewith claim 1, wherein said color-containing system is comprised of atleast one pigment and at least one thermoplastic binder or carrier.
 7. Amethod in accordance with claim 1, wherein said color-containing systemis comprised of at least one dye and at least one thermoplastic binderor carrier.
 8. A method in accordance with claim 1, wherein saidcompressive force is supplied by processing said extruded thermoplasticthrough at least one set of rolls.
 9. A method in accordance with claim1, wherein said extruded thermoplastic is maintained at a temperature inthe range of about 440° F. to about 480° F. prior to the application ofsaid color-containing system.
 10. A method in accordance with claim 1,wherein said color-containing system is maintained at a temperature inthe range of about ambient temperature to about 280° F. prior toapplication onto the surface of said extruded thermoplastic.
 11. Amethod in accordance with claim 1, wherein said color-containing systemcomprises a plurality of particles.
 12. A product prepared in accordancewith the method of claim
 1. 13. A method in accordance with claim 6,wherein said binder is a thermoplastic selected from the groupconsisting of polyacetals, acrylonitrile-styrene-acrylates,acrylonitrile-butadiene-styrenes, acrylonitrile-ethylene-styrenes,styrene-acrylonitriles, styrene-maleic anhydrides, nylons,polycarbonates, polybutylene terephthalates, polyethylenes,polypropylenes, polystyrenes, polyurethanes, polyvinyl chlorides,acrylics, and mixtures thereof.
 14. A method in accordance with claim 6,wherein said binder is a thermoplastic selected from the groupconsisting of: acrylonitrile-styrene-acrylate copolymers;acrylonitrile-butadiene-styrene copolymers;acrylonitrile-ethylene-styrene copolymers; polyvinyl chloride; blends ofpolycarbonate and acrylonitrile-butadiene-styrene copolymers in theratio of about 5:95 to about 95:5 weight percent; blends ofacrylonitrile-butadiene-styrene copolymers and nylon in the ratio ofabout 5:95 to about 95:5 weight percent; blends of polycarbonate andacrylonitrile-styrene-acrylate copolymers in the ratio of about 5:95 toabout 95:5 weight percent; blends of polyvinyl chloride andacrylonitrile-styrene-acrylate copolymers in the ratio of about 20:80 toabout 80:20 weight percent; and blends of acrylonitrile-styrene-acrylatecopolymers and acrylonitrile-ethylene-styrene copolymers in the ratio ofabout 20:80 to about 80:20 weight percent.
 15. A method in accordancewith claim 11, wherein said particles of said color-containing systemare of from about −10 to about +5000 U.S. Standard mesh size.
 16. Anapparatus for producing a granite-like appearance or other visual ortextural affect on a sheet-like molded thermoplastic product,comprising: means for extruding a sheet of thermoplastic, said sheet ofextruded thermoplastic having at least one visible surface; means forapplying at least one color-containing thermoplastic resin system tosaid visible surface of said sheet of extruded thermoplastic; and meansfor applying a compressive force to said sheet of extrudedthermoplastic.
 17. An apparatus in accordance with claim 16, furthercomprising: means for vibrating said color-containing system applicationmeans; means for metering or otherwise controlling the application ofsaid color-containing system; and means for recycling substantially allof any unapplied color-containing system.
 18. An apparatus in accordancewith claim 16, wherein said color-containing system comprises aplurality of particles.
 19. An apparatus in accordance with claim 18,wherein said particles of said color-containing system are of from about−10 to about +5000 U.S. Standard mesh size.
 20. A sheet-like moldedthermoplastic product wherein: said thermoplastic is first extruded intoa sheet having at least one visible surface; said surface having beentreated with a sufficient amount of at least one color-containingthermoplastic resin system to impart a granite-like appearance or othervisual or textural affect on said surface of said sheet of extrudedthermoplastic, said treated surface also having been exposed to acompressive force sufficient to promote adherence of saidcolor-containing resin system to said surface.
 21. A thermoplasticproduct in accordance with claim 20, wherein said extruded thermoplasticis selected from the group consisting of polyacetals,acrylonitrile-styrene-acrylates, acrylonitrile-butadiene-styrenes,acrylonitrile-ethylene-styrenes, styrene-acrylonitriles, styrene-maleicanhydrides, nylons, polycarbonates, polybutylene terephthalates,polyethylenes, polypropylenes, polystyrenes, polyurethanes, polyvinylchlorides, acrylics, and mixtures thereof.
 22. A thermoplastic productin accordance with claim 20, wherein said extruded thermoplastic isselected from the group consisting of: acrylonitrile-styrene-acrylatecopolymers; acrylonitrile-butadiene-styrene copolymers;acrylonitrile-ethylene-styrene copolymers; polyvinyl chloride; blends ofpolycarbonate and acrylonitrile-butadiene-styrene copolymers in theratio of about 5:95 to about 95:5 weight percent; blends ofacrylonitrile-butadiene-styrene copolymers and nylon in the ratio ofabout 5:95 to about 95:5 weight percent; blends of polycarbonate andacrylonitrile-styrene-acrylate copolymers in the ratio of about 5:95 toabout 95:5 weight percent; blends of polyvinyl chloride andacrylonitrilestyrene-acrylate copolymers in the ratio of about 20:80 toabout 80:20 weight percent; and blends of acrylonitrile-styrene-acrylatecopolymers and acrylonitrile-ethylene-styrene copolymers in the ratio ofabout 20:80 to about 80:20 weight percent.
 23. A thermoplastic productin accordance with claim 20, wherein the thermoplastic material for saidcolor-containing system comprises a thermoplastic binder or carriermaterial selected from the group consisting of polyacetals,acrylonitrile-styrene-acrylates, acrylonitrile-butadiene-styrenes,acrylonitrile-ethylene-styrene, styrene-acrylonitriles, styrene-maleicanhydrides, nylons, polycarbonates, polybutylene terephthalates,polypropylenes, polystyrenes, polyurethanes, polyvinyl chlorides,acrylics, and mixtures thereof.
 24. A thermoplastic product inaccordance with claim 20, wherein said binder or carrier is selectedfrom the group consisting of: acrylonitrile-styrene-acrylate copolymers;acrylonitrile-butadiene-styrene copolymers;acrylonitrile-ethylene-styrene copolymers; polyvinyl chloride; blends ofpolycarbonate and acrylonitrile-butadiene-styrene copolymers in theratio of about 5:95 to about 95:5 weight percent; blends ofacrylonitrile-butadiene-styrene copolymers and nylon in the ratio ofabout 5:95 to about 95:5 weight percent; blends of polycarbonate andacrylonitrile-styrene-acrylate copolymers in the ratio of about 5:95 toabout 95:5 weight percent; blends of polyvinyl chloride andacrylonitrile-styrene-acrylate copolymers in the ratio of about 20:80 toabout 80:20 weight percent; and blends of acrylonitrile-styrene-acrylatecopolymers and acrylonitrile-ethylene-styrene copolymers in the ratio ofabout 20:80 to about 80:20 weight percent.
 25. A thermoplastic productin accordance with claim 20, wherein said color-containing systemcomprises a plurality of particles.
 26. A thermoplastic product inaccordance with claim 25, wherein said particles of saidcolor-containing system are of from about −10 to about +5000 U.S.Standard mesh size.
 27. A thermoplastic product comprising a first layeror zone and a second layer or zone, said first layer or zone comprisingan extruded thermoplastic sheet product formed from at least onethermoplastic, and said second layer or zone comprising acolor-containing thermoplastic resin system adhering to said first layeror zone to impart a granite-like appearance or other visual or texturaleffect on a surface of said sheet of thermoplastic, saidcolor-containing system of said second layer or zone comprising at leastone pigment and at least one thermoplastic binder or carrier material,said first zone and said second zone having been compressed after saidapplication.
 28. A thermoplastic product in accordance with claim 27,wherein said extruded thermoplastic is selected from the groupconsisting of polyacetals, acrylonitrile-styrene-acrylates,acrylonitrile-butadiene-styrenes, acrylonitrile-ethylene-styrene,styrene-acrylonitriles, styrene-maleic anhydrides, nylons,polycarbonates, polybutylene terephthalates, polypropylenes,polystyrenes, polyurethanes, polyvinyl chlorides, acrylics, and mixturesthereof.
 29. A thermoplastic product in accordance with claim 27,wherein said extruded thermoplastic is selected from the groupconsisting of: acrylonitrile-styrene-acrylate copolymers;acrylonitrile-butadiene-styrene copolymers;acrylonitrile-ethylene-styrene copolymers; polyvinyl chloride; blends ofpolycarbonate and acrylonitrile-butadiene-styrene copolymers in theratio of about 5:95 to about 95:5 weight percent; blends ofacrylonitrile-butadiene-styrene copolymers and nylon in the ratio ofabout 5:95 to about 95:5 weight percent; blends of polycarbonate andacrylonitrile-styrene-acrylate copolymers in the ratio of about 5:95 toabout 95:5 weight percent; blends of polyvinyl chloride andacrylonitrile-styrene-acrylate copolymers in the ratio of about 20:80 toabout 80:20 weight percent; and blends of acrylonitrile-styrene-acrylatecopolymers and acrylonitrile-ethylene-styrene copolymers in the ratio ofabout 20:80 to about 80:20 weight percent.
 30. A thermoplastic productin accordance with claim 27, wherein said thermoplastic binder materialis selected from the group consisting of polyacetals,acrylonitrile-styrene-acrylates, acrylonitrile-butadiene-styrenes,acrylonitrile-ethylene-styrene, styrene-acrylonitriles, styrene-maleicanhydrides, nylons, polycarbonates, polybutylene terephthalates,polypropylenes, polystyrenes, polyurethanes, polyvinyl chlorides,acrylics, and mixtures thereof.
 31. A thermoplastic product inaccordance with claim 27, wherein said thermoplastic binder or carriermaterial is selected from the group consisting of:acrylonitrile-styrene-acrylate copolymers;acrylonitrile-butadiene-styrene copolymers;acrylonitrile-ethylene-styrene copolymers; polyvinyl chloride; blends ofpolycarbonate and acrylonitrile-butadiene-styrene copolymers in theratio of about 5:95 to about 95:5 weight percent; blends ofacrylonitrile-butadiene-styrene copolymers and nylon in the ratio ofabout 5:95 to about 95:5 weight percent; blends of polycarbonate andacrylonitrile-styrene-acrylate copolymers in the ratio of about 5:95 toabout 95:5 weight percent; blends of polyvinyl chloride andacrylonitrile-styrene-acrylate copolymers in the ratio of about 20:80 toabout 80:20 weight percent; and blends of acrylonitrile-styrene-acrylatecopolymers and acrylonitrile-ethylene-styrene copolymers in the ratio ofabout 20:80 to about 80:20 weight percent.
 32. A thermoplastic productin accordance with claim 27, wherein said color-containing systemcomprises a plurality of particles.
 33. A thermoplastic product inaccordance with claim 32, wherein said particles of saidcolor-containing system are of from about −10 to about +5000 U.S.Standard mesh size.